Cleaning the windows of multi-story buildings requires personnel to suspend themselves from roof tops in order to reach areas that are otherwise inaccessible. As a worker performs his duties it is necessary for him to move horizontally across the face of the building. Inventions known in the prior art facilitated this horizontal movement by attaching a scaffold to rollers that engage a track-way, gutter, or eave permanently fixed to a top portion of the side of a building.
Other inventions secure the track-way to the roof of a building. A support structure, having a boom extending over the edge of the building with a scaffold secured thereon is fixed to the track. The structure further has a means for guiding the support structure along the track. Still other inventions utilize weighted carriages having wheels thereon to support the boom structures on the roof top.
Note that the inventions of the above mentioned prior art were not designed to engage parapet walls. Indeed the boom structures supported on the roof permit the apparatus to avoid a parapet wall. There are devices in the prior art that do engage the parapet wall and utilize it as support and a runway. Such inventions in the prior art may utilize a horse-type mechanism consisting of a boom that extends over the wall and internally of the wall. The boom is supported on the parapet by a plurality of wheels and is supported on the roof by a second set of wheels, or it is tied off to the building. If it is supported on the roof by wheels, a weight is attached to its inner end to counter any tilting action. The apparatus further has outer and inner guide rollers engaging the respective surface of the wall.
Another device engaging the parapet wall utilizes a member extending along the top of the parapet wall having rollers thereon engaging the wall. A second member extends over the edge of the wall and downwardly adjacent the face of the wall, and has two rollers horizontally aligned thereon engaging the face of the wall. The second member further extends internally over the wall and downward adjacent the internal face of the wall, having rollers horizontally aligned engaging the wall upwardly offset from the external rollers.
Note in each of the devices the point of attachment of the washer's line and application of force is outward from the vertical plane defined by the wall. The force is not directly opposed, and therefore creates a tilting action into the wall that must be opposed by the force of external surface of the wall against the guide rollers. These forces against the rollers make horizontal movement difficult.
In addition, the inventions known in the prior art do not have means for the worker to climb over the wall and safely descend the wall to begin cleaning.